In the field of intelligent bathroom products, infrared sensors have been widely used in many products such as automatic faucet, auto-flushing urinal, flush toilet, toilet seat ejecting warm water, hand dryer and flush toilet with hot air fan.
The infrared sensors used in the conventional intelligent bathroom products employ an active infrared sensing method in which infrared emitters emit infrared rays of a certain wavelength, the infrared rays are reflected by human bodies and then received by infrared receivers to determine the intensity of reflected signals, thereby achieving an automatic detection. However, the automatic detection is difficult to be performed to objects with low infrared reflectivity (such as black clothes and hairs) which only reflect very few of the infrared rays to the infrared receivers. Due to insufficient intensity of the reflected signals, the sensors may fail to detect the presence of the objects, resulting in a detection failure.
In order to solve the above problem of detection failure, a PSD device has been introduced in the automatic bathroom products, wherein a PSD module in the PSD device is a photoelectrical element which is sensitive to the position of incident rays. The PSD device judges whether an object to be detected is within a predetermined range so as to controlling the water flowing and washing operations of the bathroom product. Since the PSD device implements an automatic sensing function by detecting the distance from the object instead of determining the intensity of reflected signal, it is able to overcome the defects that the conventional infrared sensing may encounter i.e. “detection failure due to reflected signals of insufficient intensity”.
However, objects which can reflect rays efficiently and have high reflectivity, such as mirror and stainless steel door, are prohibited from being installed opposite to the PSD device, because the PSD device, when receiving the reflected infrared signals with relatively high intensity, may accordingly perform preset operations such as water flowing and washing operations. Therefore, objects with high reflectivity, if located opposite to the PSD device, tend to result in mis-operation of the PSD device.
At present, solutions adopted to solve this problem typically involve preventing objects with high reflectivity being installed opposite to the PSD device, or installing the PSD device obliquely so that rays can not be reflected to the receiver by a vertical object with high reflectivity. The above two solutions, however, limit the application of the sensor, poses more demands to the application environment and limit the mechanical structure of the product.
Accordingly, it is a common concern in the field on how to effectively solve the problem in the PSD device that the PSD device is mis-operated due to the mirror reflection.